This invention relates to heat treatable low emissivity (low-E) coated articles, and methods of making the same. Such coated articles may be used in the context of vehicle windshields, insulating glass (IG) units, other types of architectural and/or vehicle windows, and other suitable applications.
Layer coatings provided for solar management purposes are known in the art. Such coatings often seek to reflect significant amounts of infrared (IR) radiation while at the same time enabling a high amount of visible light transmittance. High visible transmittance is often desired, and this need often conflicts with the need for good IR reflection, and it is difficult to obtain both simultaneously. It is also desirable for such coatings to be heat treatable in some instances, so that they may be used in vehicle windows where heat bending is required, tempered architectural or vehicle windows, and/or the like.
WO 02/04375 discloses a low-E coating including the following layers: glass/TiOx/SixNy/NiCrOx/Ag/NiCrOx/SnOx/SixNy/NiCrOx/Ag/NiCrOx/SnOx/SixNy. The metallic Ag layers are sputtered in an argon (Ar) gas atmosphere, as is typical in the art. This low-E coating provides for excellent solar performance and is an overall good coating. However, it has been found that this coating is subject to scratching during, for example, pre-final-product processing (e.g., before heat treatment).
In view of the above, it will be apparent to those skilled in the art that there exists a need in the art for a low-E coating that is more mechanically durable and thus less susceptible to scratching and the like, and/or which is more thermally stable (i.e., does not suffer a radical drop in visible transmission upon heat treatment such as tempering).
An object of certain example embodiments of this invention is to provide a more durable coating that is less susceptible to scratching and/or other types of mechanical damage, and/or which has improved thermal stability.
Surprisingly, it has been found that sputtering the Ag inclusive layers of the aforesaid coating in an atmosphere not simply including Ar gas, but also including oxygen gas (O2), renders the resulting coating (a) more mechanically durable and less susceptible to scratching, and/or (b) acceptably thermally stable. For example, it has been found that sputtering at least one of the Ag inclusive layers of the aforesaid coating in an atmosphere including a combination of Ar/O2 gas leads to a more durable without sacrificing thermal stability.
U.S. Pat. No. 5,584,902 discloses a low-E coating system including, from the glass substrate outward, a stack of: Si3N4/NiCr/Ag/NiCr/Si3N4. Like most other prior art, the Ag layer of the ""902 patent is preferably sputtered in an Ar gas atmosphere (e.g., see col. 16, lines 33-45). However, the ""902 Patent does mention at col. 12, lines 59-63, that each of the three metallic layers NiCr/Ag/NiCr may be sputtered optionally in an atmosphere including xe2x80x9ca small amount of O2 (e.g. about 5-10%).xe2x80x9d However, this means that all three layers (NiCr, Ag and NiCr) are sputtered in the same atmosphere, and that each atmosphere includes the same amount of oxygenxe2x80x94this is undesirable in many instances. While the ""902 coating is heat treatable and low-E in nature, it is characterized by rather high emissivity and/or sheet resistance values which lead to rather low Rsolar (total solar energy reflectance) values around 22-24%. For example, one coating reported in the ""902 patent had a sheet resistance (Rs) of 14.4 ohms/square and a normal emissivity (En) of 0.15 before heat treatment; and a Rs of 10.5 ohms/square and a En of 0.11 after heat treatment. Moreover, there is no disclosure or suggestion in the ""902 Patent that sputtering an Ag target in an atmosphere including oxygen can lead to improved mechanical durability and/or thermal stability.
As explained above, an object of certain embodiments of this invention is to provide a more durable low-E coating that is less susceptible to scratching and/or other types of mechanical damage, and/or which has improved thermal stability. This object may be fulfilled by sputtering at least one Ag inclusive layer in an atmosphere including O2 gas (e.g., a combination of Ar and O2 gas may be used). The use of oxygen gas proximate the Ag sputtering target is especially beneficial in this respect when one or more of the immediately adjacent contact layers is/are significantly oxidized (e.g., when one or both of the adjacent contact layers comprises NiCrOx).
Another object of certain exemplary embodiments of this invention is to provide a dual silver low-E coating which is heat treatable and is mechanically and/or chemically durable.
Another object of certain exemplary embodiments of this invention is to provide a heat treatable low-E coating having high visible transmittance (e.g., of at least about 65%) combined with a normal emissivity (En) of no greater than 0.08 (more preferably no greater than 0.06) before heat treatment, and/or an En of no greater than 0.07 (more preferably no greater than 0.05) after heat treatment (HT).
Another object of certain exemplary embodiments of this invention is to provide a heat treatable low-E coating having high visible transmittance combined with a sheet resistance (Rs) of no greater than 10.0 ohms/sq. (more preferably no greater than 8.0 ohms/sq., and most preferably no greater than about 5.0 ohms/sq.) before heat treatment; and/or a Rs of no greater than 8.0 ohms/sq. (more preferably no greater than 6.0 ohms/sq., and most preferably no greater than about 4.0 ohms/sq.) after heat treatment.
Another object of this invention is to fulfill one or more of the above-listed objects.
Generally speaking, certain example embodiments of this invention fulfill one or more of the above-listed objects by providing a method of making a coated article including a coating supported by a glass substrate, the method comprising: sputtering a first dielectric layer so as to be supported by the glass substrate; sputtering a first contact layer on the substrate over the first dielectric layer; sputtering a target comprising Ag in an atmosphere including at least oxygen gas in order to form an infrared (IR) reflecting layer comprising AgOx which is located over and contacts the first contact layer; sputtering a second contact layer on the substrate so that the second contact layer is located over and in contact with the IR reflecting layer comprising AgOx; and wherein said sputtering of at least one of the contact layers comprises sputtering a target comprising a metal or metal alloy in an atmosphere including at least oxygen gas in order to form a metal oxide contact layer, and wherein more oxygen gas is introduced into an atmosphere used in sputtering the metal oxide contact layer than is introduced into an atmosphere proximate the target comprising Ag used in sputtering the IR reflecting layer comprising AgOx. In one example embodiment, oxygen may be fed into the neighboring cathode bay instead of directly into either the contact layer or IR reflecting layer bays; oxygen would thereby enter into the contact layer and/or IR reflecting layer bay(s)s by diffusion.
Certain other example embodiments of this invention fulfill one or more of the above-listed objects by providing a coated article including a coating supported by a glass substrate, the coating comprising: a first dielectric layer supported by the glass substrate; a first contact layer comprising a metal oxide provided on the substrate over the first dielectric layer, wherein a central portion of the first contact layer is at least about 40% oxidized; an IR reflecting layer comprising AgOx contacting the first contact layer, wherein the first contact layer is either above or below the IR reflecting layer on the substrate; and at least one dielectric layer provided on the substrate over the IR reflecting layer and the first contact layer.
Certain other example embodiments of this invention fulfill one or more of the above-listed objects by providing a coated article including a coating supported by a glass substrate, the coating comprising: a first dielectric layer supported by the glass substrate; an optional first contact layer comprising a metal oxide provided on the substrate over the first dielectric layer, wherein a portion of the first contact layer is at least about 40% oxidized; an IR reflecting layer comprising AgOx contacting the first contact layer or the bottom dielectric layer, an optional contact layer above the IR reflecting layer; and at least one dielectric layer provided on the substrate over the IR reflecting layer contacting directly either the IR reflecting layer or the optional contact layer.
This invention will now be described with respect to certain example embodiments thereof as illustrated in the following drawings, wherein: